The present invention relates to control apparatus for remotely activating the transmitter of an impact sensor system. More particularly, it concerns circuitry which prevents inadvertent emissions from a remotely activated transmitter until it has been commanded into two successive operative modes and has also received two reset commands, as will be explained in detail below.
Signal transmission systems are often used in remote locations to monitor various phenomena occurring in the vicinity of the system, such as motion, temperature and pressure changes and the like. One such application concerns the monitoring of a sensor adapted to detect stresses, strains and impacts upon a satellite carried into space and launched into orbit by a manned spacecraft, such as the space shuttle.
It is important for safety reasons that the transmitter associated with such an impact sensor system not be inadvertently activated while traveling as cargo in the space shuttle. After the satellite has been launched into orbit, a transmitter turn-on command is sent to the satellite by the spacecraft. The initial operative mode in which the impact sensor system is placed however, is completely random and if the command happens to place the impact sensor to an in-flight test mode or alarm mode, the transmitter would broadcast. Therefore a first fault that could possibly occur which could cause the impact sensor transmitter to broadcast is the presence of a false or unintended spacecraft command. A second fault that could possibly occur which would also cause the transmitter to erroneously broadcast concerns a defective component in the logic circuitry to the transmitter power switch or a defect in the power switch itself.
It is accordingly an object of the present invention to provide a two fault tolerant transmitter activator.
It is a more specific object of the invention to provide means for inhibiting transmissions from a remotely activated impact sensing transmitter until the transmitter has been found to be free of specific operative faults.